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INSTRUCTION SET
LDCD/LDED
LDCD/LDED
dst,src
dst ← src
Operation:
rr ← rr – 1
These instructions are used for user stacks or block transfers of data from program or data
memory to the register file. The address of the memory location is specified by a working register
pair. The contents of the source location are loaded into the destination location. The memory
address is then decremented. The contents of the source are unaffected.
LDCD references program memory and LDED references external data memory. The assembler
makes 'Irr' an even number for program memory and an odd number for data memory.
Flags:
No flags are affected.
Format:
opc
Examples:
Given: R6 = 10H, R7 = 33H, R8 = 12H, program memory location 1033H = 0CDH, and
external data memory location 1033H = 0DDH:
LDCD
LDED
6-54
— Load Memory and Decrement
dst | src
R8,@RR6
; 0CDH (contents of program memory location 1033H) is loaded
; into R8 and RR6 is decremented by one
; R8 = 0CDH, R6 = 10H, R7 = 32H (RR6 ← RR6 – 1)
R8,@RR6
; 0DDH (contents of data memory location 1033H) is loaded
; into R8 and RR6 is decremented by one (RR6 ← RR6 – 1)
; R8 = 0DDH, R6 = 10H, R7 = 32H
S3C8248/C8245/P8245/C8247/C8249/P8249
Bytes
Cycles
Opcode
2
10
Addr Mode
(Hex)
dst
src
E2
r
Irr
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